Legionnaires' disease prevention

Reducing the risk of Legionnaires’ disease around the home

You can reduce the risks of legionella infection Legionnaires' disease by taking some simple steps when installing and maintaining water pipes, plumbing fittings and some water filled appliances/fixtures such as hot water systems (including solar), rainwater tanks, bores, pools, spas and air conditioners. Care should also be taken when handling soil and potting mix, and after flooding.

Hot water systems

Hot water systems, (including shower roses, hot water taps, hot water tanks, pipework and the associated fittings) have the potential to harbour the Legionella bacteria where there may be stagnant or warm water (25-50°C). The following precautions will help reduce the risk:

• Hot water tanks are required by Queensland law to store water at 60°C or more to reduce the risk of Legionella multiplying in the hot water system and plumbing. However this temperature may cause scalding so water used for washing and bathing should be delivered at 45-50°C through the use of water temperature controllers such as thermostatic mixing valves or thermostats that can be regulated (for instantaneous water heaters). Do not turn down hot water systems. Any adjustment to the thermostat settings should be done by a licensed electrician.
• Hot water systems should not be turned off unnecessarily. Boosters for solar hot water systems should not be turned off during cloudy days. Hot water systems that are turned on after prolonged absences from home should heat water to 60°C for at least half an hour prior to use of the hot water.
• Each week flush all hot and mixed showers and taps that have not been used with hot water at full flow for at least 15 seconds. Flushing will help eliminate stagnant water and minimise the multiplication of bacteria that may be present. Showers and taps that are not used for extended periods of time (e.g. due to absence from home) require longer flushing to remove the stagnant water from the pipes. Caution should be given when flushing to prevent inhalation of the water aerosols (tiny airborne water droplets).
• Maintain your hot water systems. Use a registered plumber and refer to manufacturer’s instructions or check the manufacturer’s website for information.

Private water supplies: rainwater tanks or bore water

Private bores or river off-take water supplies may encourage the growth of Legionella in their storage or reticulation systems.

Watch for elevated water temperature, high organic or mineral content in the water, or accumulated sediment in storage tanks.

Rainwater tanks need to be well designed and carefully cleaned and maintained to reduce the risk of Legionella.

Read more about the guidelines for use of rainwater tanks.

Domestic air conditioners

Domestic air conditioners (refrigerated/reverse cycle integrated and split systems that remove heat and moisture from the air without using water) do not harbour Legionella bacteria.

Evaporative air conditioners use water to cool air. There have been no reported cases of Legionnaires disease caused by these appliances (built-in or portable), but there are some steps you can take to reduce risks:

• follow the manufacturer’s maintenance and cleaning instructions
• use a clean and fresh water supply
• contact an air conditioning company for regular cleaning and maintenance services.

Home pools and spas

Domestic pools represent a low risk because they do not generate aerosols however Legionella can multiply in the jets, pipes and pumps of home pools and spas if biofilm (slimy growths of bacteria, protozoa, algae and fungi) is allowed to form. Spas require careful maintenance, disinfection and frequent cleaning because the warm water is ideal for bacterial growth and they generate aerosols (tiny airborne water droplets) that can be inhaled.

Read more about maintaining private spa pools (PDF, 111kb).

For spa baths, use commercial products formulated especially for cleaning spa baths, or you can use a low foaming detergent and/or a mild bleach.

Check with the manufacturer for the recommended method of cleaning your spa bath.

Soil and potting mix

Legionella longbeachae (a different strain of the legionella bacteria) is common in the soil and potting mix. Infection with this organism can also cause Pontiac fever (another form of  Legionellosis).

Reduce your exposure to potting mix dust by:

• wetting down the potting mix to reduce dust
• wearing gloves and a class P2 dust mask when using potting mix
• washing your hands after handling potting mix or soil, and before eating, drinking or smoking
• following the manufacturers' warnings present on potting mix labels.

Flood recovery

After flooding, plumbing fittings may require cleaning to remove any matter that may lead to biofilm formation and allow Legionella to multiply. Follow any instructions of your water service provider regarding the boiling of water and flushing of taps and showerheads in the home.

If the house has been inundated, extra care may be needed to ensure the plumbing is clean and safe.

If in doubt, contact a licensed plumber or your local council.

More information on staying safe and healthy in disaster events.

More information

Contact your nearest Queensland Health Public Health Unit (business hours, Monday to Friday).